So much information here...before its stated - yes i have searched and read just about every 40hp build post. So many options and variables I want opinions on what I am planning.

Some background: its a '65 40HP that is pushing a Manx clone buggy sitting on a '62 swing axel pan. I purchased the buggy in 2014 and have been driving it ever since. I am slowly going through the entire pan (brakes, electrical, etc.). I am adding a roll cage this winter so with the added weight thought I would "refresh" the motor and give it a bit more pep. P.O. stated the 40HP was stock.

Questions:
- Rocker arms - stick with the 1:1 or go with 1.25:1?
- Any need to go solid shaft?
- Carb- have a Solex 28 Pict-1 with 122.5 main jet. Upgrade to 125 , 130 or 135? Or better to get a new carb all together? 30 Pict, 34 Pict, H31/31?

This is a 3 season (do all my work in winter and enjoy it the rest of the year) weekend driver and occasional afternoon driver. Want to give the buggy a bit more go without breaking the bank.

You'll be money ahead, and ultimately make more power with greater reliability, if you save your 40 horse for a "spare" and rebuild a 1600 dual port.
The 40 horse has "modest" potential, but will cost more to achieve power equal to the 1600 and will require you to fabricate and improvise to a much greater degree. Some of us enjoy such challenges, but do you?
If so, get the 83mm p&c's. Get a pair of 1500 single port heads to rebuild and do a few performance upgrades, flycut for more compression, shorten a Zenith single carb and intake to fit, add a 1 3/8 four-into-one header, add closer ratio 3rd and 4th to the transaxle (NOT A FREEWAY FLYER!!), and enjoy it.
Rock on.

You'll be money ahead, and ultimately make more power with greater reliability, if you save your 40 horse for a "spare" and rebuild a 1600 dual port.
The 40 horse has "modest" potential, but will cost more to achieve power equal to the 1600 and will require you to fabricate and improvise to a much greater degree. Some of us enjoy such challenges, but do you?
If so, get the 83mm p&c's. Get a pair of 1500 single port heads to rebuild and do a few performance upgrades, flycut for more compression, shorten a Zenith single carb and intake to fit, add a 1 3/8 four-into-one header, add closer ratio 3rd and 4th to the transaxle (NOT A FREEWAY FLYER!!), and enjoy it.
Rock on.

So eventually there is a 1600dp but I got to learn with what I got. I do have a budget of $600 to get this engine refreshed. $600 won't get me a running 1600dp. I absolutely enjoy the challenges and it's my passion to tinker with everything. The 40hp build is just to wet my appetite and get more pep. Hay being said- do the above "bolt on" upgrades- going down the right track??

I have that set up in my 65. Verify that you have the square boss 65 heads ( I dont remember the casting number, but its on here). I am running a 28PICT1 and ended up with 130 mains and 50 idles (tuned on a chassis dyno). Using an 019 mechanical becasue at the time I was having a hard time finding the correct vacuum distributor. An 009 ran "OK" but the 019 was much smoother and overall nicer.

Your rear tire size will somewhat dictate what you want to do with your tranny. With the stock tires on my 65, it pulls real strong, but I am top end limited. Don't like taking it above 70 for any length of time (usually just to pass). Usual cruise speed is 65.

We have a buggy and had the stock 63 transaxle in it originally, but went from a 1600 to a 1776 and then a 1914. Had the tranny rebuilt with 3.88 (I think) R/P. Was spinning way to fast at highway speeds.

I have that set up in my 65. Verify that you have the square boss 65 heads ( I dont remember the casting number, but its on here). I am running a 28PICT1 and ended up with 130 mains and 50 idles

...

a 28 PICT1 has an idle jet?? Is it referred to as the pilot jet (#16) here (http://www.vw-resource.com/28carb.html)

andk5591 wrote:

Using an 019 mechanical becasue at the time I was having a hard time finding the correct vacuum distributor. An 009 ran "OK" but the 019 was much smoother and overall nicer.
...

Good to know...I have a mechanical 009 on there now. Will see how it does post mods.

andk5591 wrote:

Your rear tire size will somewhat dictate what you want to do with your tranny. With the stock tires on my 65, it pulls real strong, but I am top end limited. Don't like taking it above 70 for any length of time (usually just to pass). Usual cruise speed is 65. ...

Rears are 15x255 fronts are 15x215, but the tranny is stock. I don't really plan to be doing a lot of highway driving but having some pep to pass and keep up with traffic would be great.

And so the snowball begins to roll...
Sure, splitting the case is a great idea. It will be a perfect time to put in a cam & lifters (CB 2280) and swap in a 69mm crank from a 1500/1600 and new bearings (machine the sides of the rods and get it all balanced so the different gears in the transaxle don't become tiresome...). Oh, and here is where you start throwing another $600 at it...and now you have 1500cc's and the $$ investment that should've gotten you the 1600 dualport we talked about earlier.
Where do you start? Where do you stop? How much is enough?

Your rear tire diameter difference will net about a 9 MPH change. Will let you do the math to see what the RPM difference will be. And also take into account your front tire diameter will impact speedometer accuracy.

And so the snowball begins to roll...
Sure, splitting the case is a great idea. It will be a perfect time to put in a cam & lifters (CB 2280) and swap in a 69mm crank from a 1500/1600 and new bearings (machine the sides of the rods and get it all balanced so the different gears in the transaxle don't become tiresome...). Oh, and here is where you start throwing another $600 at it...and now you have 1500cc's and the $$ investment that should've gotten you the 1600 dualport we talked about earlier.
Where do you start? Where do you stop? How much is enough?

LOL - exactly. I'm not looking to upgrade any internal unless things look bad. I thought using the 1.25 rockers is "synonymous" to a mild cam since I would get "taller" valve opening - or at least that is what I read during research.

I'm trying really hard to not make this a rabbit hole I lose myself in and stick to my budget.

Your rear tire diameter difference will net about a 9 MPH change. Will let you do the math to see what the RPM difference will be. And also take into account your front tire diameter will impact speedometer accuracy.

Bottom line is that with as tall a tire that you have, I would not change the final ratio in the tranny.

Can you point me in the right direction on where you are doing these calculations? There an online calculator?

Quick and dirty way to get engine rpm based on a road speed and your gear ratios:

mph * 336 / tire_height * ring&pinion * gear = rpm

To get speed from at an rpm and gear:

rpm / gear / ring&pinon * tire_height / 336 = mph

If any of the units above are unclear let me know and I'll clarify. Tire height is standing height in inches, stock is about 25.4 inches.

excellent, thanks. does the width of tire matter? height always in inches? Also ring&pinion...where would I get that info? Its a stock swing axel tranny. I believe a '62. I'll have to double check the stamped number on the tranny. Im pretty comfortable with engine but still dont have courage to work on tranny

The width of the tire does not matter. For that formula to work it is the tire height in inches.

Transaxle gear ratios can be hard to determine because so much as been rebuilt and modified over the years. From 1961 through 1965 the Beetles sold in the U.S. all had the 40 horse engine and the same transaxle gearing:

Since 1.1:1 13-1600 rockers are dirt cheap and an easy bolt on I don't see any reason not to use them. I wouldn't use 1.25's unless you already have them. 40hp heads (and a stock carb/intake) only flow so much air, more lift does not necessarily mean more power. I would also be very cautious about increasing camshaft duration with the stock intake and carb._________________EMPI Power Rules!